Fuel injection valve

ABSTRACT

A fuel injection valve including a pan-shaped protective cap having a radially outwardly extending recess which, together with the fuel injection valve, forms a gap which is so narrow that it exerts a capillary effect on the fuel so that, when the internal combustion engine is shut down, the high boiling point constituents of the fuel are deposited at the radial outer edge of the gap, because of the capillary effect, and the injection openings remain free from deposits. The protective cap of the invention has at least three protrusions formed from its bottom and protruding in the direction of the fuel injection valve to a predetermined axial distance, the protrusions of the protective cap being in contact with the orifice plate of the fuel injection valve, forming an axial gap in a simple manner between the bottom and the orifice plate. The protective cap can be used with fuel injection valves of various types.

STATE OF THE ART

The invention is based on a fuel injection valve as set forth herein. Inthe German patent application P 39 27 390.3, a fuel injection valve hasalready been proposed in which a pan-shaped protective cap is provided.This cap has a passage opening in its bottom downstream of the at leastone injection opening. The protective cap is intended to prevent damagein the region of the at least one injection opening and to avoidparticles from the surroundings of the fuel injection valve, whosenozzle body protrudes into the induction pipe, from being deposited inthe region of the at least one injection opening and leading to arestriction of the at least one injection opening. Such restrictionwould reduce the quantity of fuel injected in an undesirable manner. Thenarrow gap formed, by a contact section of the protective cap, betweenthe bottom of the protective cap and an end surface of the fuelinjection valve ensures that even in the case of fairly long periods ofoperation of the internal combustion engine, fuel deposits caused by thesequential operating and shut-down phases do not lead to the fuelquantity metered by the fuel injection valve being reduced in anundesirable manner.

If the internal combustion engine (and therefore also the fuel injectionsystem) is shut down, the fuel injection valve is closed and fuelpossibly present in the gap and the passage opening partially evaporatesbecause of the strong heating from the internal combustion engine. Inthis process, only the constituents of the fuel which evaporate atrelatively low temperatures are volatilised whereas the constituentswhich evaporate at higher temperatures are not sufficiently heated andmove outwards in the gap in the radial direction because of thecapillary effect of the narrow gap and are deposited there so that theat least one injection opening and the passage opening remain free fromdeposits.

Exact axial adjustment of the narrow gap, such as is necessary for thecapillary effect, is not, however, always guaranteed by the contactsection of the protective cap in accordance with the German patentapplication P 39 27 390.3. In addition, the manufacture of theprotective cap is complicated for mass production purposes.

ADVANTAGES OF THE INVENTION

The fuel injection valve according to the invention has an advantage ofsimple and low-cost manufacture and the possibility of exact axialadjustment of the narrow gap, this exact adjustment being achieved in asimple manner by the protrusions. The narrow gap formed between thebottom of the protective cap and the end surface of the fuel injectionvalve exerts a capillary effect on the fuel and, in the case of fairlylong periods of operation of the internal combustion engine, reliablyprevents undesirable reduction by fuel deposits of the free flowcross-section of the at least one injection opening and the passageopening and, therefore, of the fuel quantity metered by the fuelinjection valve. Advantageous extensions and improvements to the fuelinjection valve given herein are possible by means of the measureslisted.

It is of advantage for the protective cap to have a retention collarwith at least two dimples formed in it protruding radially outwards atits end remote from the bottom. These dimples act to increase thestrength of the retention collar, which acts as the side surface for asealing ring.

It is particularly advantageous for the protective cap to be formed froma metallic material. The evaporation of the low boiling-pointconstituents of the fuel, which occurs after the internal combustionengine is shut down, and hence the deposit of the higher boiling-pointconstituents is substantially reduced by utilising the condensationeffects of the fuel on the metallic protective cap.

For particularly simple and low-cost manufacture of the fuel injectionvalve according to the invention, it is advantageous for the protectivecap to be formed by shaping sheet metal.

For a connection between the protective cap and the nozzle body which isreliable and can be manufactured in a simple manner, it is advantageousfor the protective cap to be connected to the nozzle body byindentation.

For the same reason, it is also advantageous for at least two inwardlyprotruding engagement steps or at least two inwardly protrudingretention tongues to be formed on the periphery of the protective cap,these steps or tongues engaging in an annular groove of the nozzle body.

DRAWING

Illustrative examples of the invention are shown in a simplified mannerin the drawings and are explained in more detail in the followingdescription.

FIG. 1 shows a first illustrative example of a fuel injection valveembodied according to the invention;

FIG. 2 shows a view in the direction of the arrow X in FIG. 1 of theprotective cap in accordance with the first illustrative example.

FIG. 3 illustrates a second illustrative example of a modified fuelinjection valve;

and FIG. 4 is a view in a direction of the arrow X of FIG. 3 of theprotective cap for the modification shown in FIG. 3.

DESCRIPTION OF THE ILLUSTRATIVE EXAMPLES

The fuel injection valve shown in a partial view in FIG. 1 agreesessentially with a fuel injection valve for a fuel injection system of amixture-compressing externally-ignited internal combustion enginedescribed in DE-OS 37 10 467 and is used, for example, for fuelinjection into the induction pipe of the internal combustion engine Anozzle body 1, in which a valve needle 3 is guided in a guide opening 2,is connected to a valve housing, which is not shown. The guide opening 2ends, in the nozzle body 1 shown, in an undercut 5 which is followed, inthe flow direction of the fuel, by a conically narrowing valve seatsurface 8. A cylindrical transition opening 11 extends between the valveseat surface 8 and a nozzle body end surface 9 of a nozzle body end 10.In the region of the valve seat surface 8 of the nozzle body 1, thevalve needle 3 merges into a sealing seat 12 conically narrowing in thedirection of the nozzle body end surface 9, the sealing seat 12 beingterminated by a cylindrical spigot 13.

In the closed condition of the fuel injection valve, the sealing seat 12of the valve needle 3 is in contact with the valve seat surface 8whereas, in the open condition of the fuel injection valve, the sealingseat 12 is raised from the valve seat surface 8 and fuel can flow to thetransition opening 11. A thin orifice plate 15 is tightly connected tothe nozzle body end surface 9 by welding or brazing, for example. Thisorifice plate 15 has, in its region covered by the transition opening11, at least one injection opening 16 used for fuel metering. The twoinjection openings 16, shown as an example, penetrate the orifice plate15 and are inclined, in the illustrative example shown, relative to avalve longitudinal axis 17. Depending on the type of use, they can beinclined in such a manner that the fuel jets emerging from theindividual injection openings 16 are either directed inwards towards thevalve longitudinal axis 17 or outwards away from the valve longitudinalaxis 17. When the fuel injection valve is open, the quantity of fuelinjected per unit time is metered by the cross-section of the injectionopenings 16. The opening of the fuel injection valve takes placeelectromagnetically, in a manner not shown.

The, for example, two injection openings 16 are arranged in the orificeplate 15 in such a way that they emerge from the annular space formedbetween the spigot 13 of the valve needle 3 and the wall of thetransition opening 11, the cylindrical spigot 13 protruding almost ontothe orifice plate 15 when the fuel injection valve is closed.

Pushed onto the nozzle body end 10, there is a protective cap 20 ofpan-shaped design which partially surrounds the nozzle body 1 in theaxial direction with a cylindrical shell 21.

As is indicated in the first illustrative example of the invention,shown in FIG. 1 but also in FIG. 2, which shows a view of the protectivecap 20 according to the first illustrative example in the direction ofthe arrow X in FIG. 1, four (for example) inwardly directed engagementsteps 22 are formed on the cylindrical shell 21 of the protective cap 20and engage in an annular groove 23 of the nozzle body 1 extending, forexample, peripherally and so act to fix the position of the protectivecap 20 on the nozzle body 1. It is, however, also possible for theprotective cap 20 to be connected to the nozzle body 1 by indentation ofthe material of the protective cap 20 in the region of the annulargroove 23 of the nozzle body 1 in such a way that, for example, aperipheral retention collar of the protective cap 20 engages in theannular groove 23 of the nozzle body 1.

In a second illustrative example of the invention, which is shown inFIGS. 3 and 4 which differs from the first illustrative example only bythe type of connection between the protective cap 20 and the nozzle body1, at least two inwardly protruding retention tongues 25 are formed forthis purpose on the cylindrical shell 21, these retention tongues 25engaging in the, for example, peripheral annular groove 23 of the nozzlebody 1.

A bottom 28 of the protective cap 20 has, concentric with the valvelongitudinal axis 17, a passage opening 29 and extends in the radialdirection beyond the orifice plate 15 to the cylindrical shell 21. Atleast three protrusions 30 are formed from the bottom 28. These areequally spaced and protrude by a predetermined axial distance 31 in thedirection of the nozzle body end 10 of the nozzle body 1. In FIGS. 2 and4, four protrusions 30 are shown as an example. The protective cap 20 isin contact with the orifice plate 15 of the fuel injection valve bymeans of flat or sharp-edged contact surfaces 32 of the protrusions 30.In this way, an annular gap 36 is formed between the bottom 28 of theprotective cap 20 and the end surface 35, of the fuel injection valve,formed by the orifice plate 15. Because of the predetermined axialdistance 31 by which the protrusions 30 protrude from the bottom 28,this annular gap 36 has an exactly definable extension in the directionof the valve longitudinal axis 17. The axial distance 31, and thereforethe axial extension of the gap 36, is small relative to the diameter ofthe passage opening 29 of the protective cap 20. The gap 36 issubdivided into sectors by the protrusions 30.

Because of the small axial distance 31, the annular gap 36 exerts,whatever the opening condition of the fuel injection valve, such a largecapillary effect on the fuel that the fuel present in the gap 36 doesnot flow out of the passage opening 29 because of its weight. The narrowgap 36 can, starting from the passage opening 29, extend with increasingradial direction in such a way that it either narrows or widens in theaxial direction. If the internal combustion engine, and therefore alsothe fuel injection system, is shut down, the fuel injection valve isclosed and fuel possibly present in the gap 36 and the passage opening29 partially evaporates because of the strong heating from the internalcombustion engine; only the constituents of the fuel evaporating atrelatively low temperatures are volatilised whereas the constituentsevaporating at higher temperatures are not sufficiently heated and moveradially outwards in the annular gap 36 because of the capillary effect.These constituents are then deposited on the wall 38 of the cylindricalshell 21 so that the passage opening 29 and the orifice plate 15 remainfree from fuel deposits in the region of, for example, the two injectionopenings 16.

At its end remote from the bottom 28, the protective cap 20 has aretention collar 40 pointing radially outwards. Four, for example,dimples 41 are formed in the retention collar 40; they are used toincrease the strength of the retention collar 40 and protrude from theretention collar 40 with an axial distance 42 in the direction towardsthe bottom 28 of the protective cap 20.

Both the protrusions 30 and the dimples 41 can, in addition to thecircular shape shown in the two illustrative examples, be formed in anyother given shape, for example oval, rectangular, notch-shaped orannular.

The end surface 43 of the retention collar 40 remote from the bottom 28,together with a retention ring 45, which is located on the periphery ofthe nozzle body 1 remote from the nozzle body end 10, form the sidesurfaces of an annular groove 46 whose groove bottom 47 is formed by theperiphery of the nozzle body 1. Located in the annular groove 46, thereis a sealing ring 48 which permits reliable and safe sealing between thenozzle body 1 of the fuel injection valve and a valve location feature(not shown) which surrounds the fuel injection valve.

The protective cap 20 is formed, for example, from a metallic material.Because of the thermal conductivity of metallic materials, which isgenerally higher compared with plastics, and the associated improvedheat removal of a metallic protective cap 20, condensation effectsacting on the fuel occur. After the internal combustion engine (andhence also the fuel injection system) has been shut down, therefore, theevaporation of the low boiling-point constituents of the fuel issubstantially reduced and with it, the deposition of the higherboiling-point constituents in the annular gap 36. The danger of depositsin the region of the two, for example, injection openings 16 and thepassage opening 29 of the protective cap 20 is additionally furtherreduced.

Simple and low-cost manufacture of a metallic protective cap 20according to the invention is made possible by forming the protectivecap 20, including the protrusions 30, the retention collar 40 and thedimples 41, by sheet metal shaping. The thickness of the sheet metal tobe shaped is, for example, 0.5 mm. It is, however, also possible to formthe metal protective cap 20 by machining.

The protective cap 20 fastened to the nozzle body 1 of the fuelinjection valve not only acts to protect the at least one injectionopening 16 from damage and from the deposit of particles but acts alsoto avoid deposits of higher boiling-point constituents of the fuel inthe region of the at least one injection opening 16 and the passageopening 29 because the narrow annular gap 36 exerts a capillary effecton the fuel and the higher boiling-point constituents of the fuel aredeposited in this gap.

The foregoing relates to a preferred exemplary embodiment of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

We claim:
 1. A fuel injection valve having a nozzle body, a one-piecepan-shaped protective cap fastened to said nozzle body, said pan-shapedprotective cap is provided with a bottom which has a passage openingextending approximately concentrically about a longitudinal axis of saidfuel injection valve and opens towards at least one fuel injectionopening, at least one gap formed between the bottom of the protectivecap and an end surface of the fuel injection valve, said at least onegap opens toward the passage opening, the protective cap (20) isprovided with at least three axially directed protrusions (30) formed asa part of the bottom (28) and which protrudes with a predetermined axialdistance (31) in a direction of the fuel injection valve for contactwith the end surface (35) of the fuel injection valve.
 2. A fuelinjection valve according to claim 1, in which the protective cap (20)has a radially outwards protruding retention collar (40) spaced axiallyfrom the bottom (28), in which at least two dimples (41) are formed. 3.A fuel injection valve according to claim 2, in which the axial distance(31) is small relative to the diameter of the passage opening (29) ofthe protective cap (20).
 4. A fuel injection valve having a nozzle body,a thin orifice plate (15) tightly secured to an outlet end of saidnozzle body, said thin orifice plate including at least one fuelinjection opening (10), a pan-shaped protective cap fastened to saidnozzle body, said pan-shaped protective cap is provided with a bottomwhich has a passage opening extending approximately concentrically abouta longitudinal axis of said valve and opens towards said at least onefuel injection opening, at least one gap formed between the bottom ofthe protective cap and said thin orifice plate secured to an outlet endsurface of the fuel injection valve, said at least one gap opens towardthe passage opening, the protective cap (20) is provided with at leastthree axially directed protrusions (30) formed from the bottom (28) andprotruding with a predetermined axial distance (31) in a direction ofthe fuel injection valve in contact with the thin orifice plate securedto an outlet end surface (35) of the fuel injection valve.
 5. A fuelinjection valve according to claim 4, in which the protective cap (20)has a radially outwards, protruding retention collar (40) spaced axiallyfrom the bottom (28), in which at least two dimples (41) are formed. 6.A fuel injection valve according to claim 4, in which the gap (36) issubdivided into sectors by the protrusions (30).
 7. A fuel injectionvalve according to claim 6, in which the protective cap (20) has aradially outwards protruding retention collar (40) spaced axially fromthe bottom (28), in which at least two dimples (41) are formed.
 8. Afuel injection valve according to claim 7, in which the axial distance(31) is small relative to the diameter of the passage opening (29) ofthe protective cap (20).
 9. A fuel injection valve according to claim 8,in which the axial distance (31) is small relative to the diameter ofthe passage opening (29) of the protective cap (20).
 10. A fuelinjection valve according to claim 4, in which the protective cap (20)is formed from a metallic material.
 11. A fuel injection valve accordingto claim 10, in which the axial distance (31) is small relative to thediameter of the passage opening (29) of the protective cap (20).
 12. Afuel injection valve according to claim 4, in which the protective cap(20) is formed by sheet metal shaping.
 13. A fuel injection valveaccording to claim 12, in which the axial distance (31) is smallrelative to the diameter of the passage opening (29) of the protectivecap (20).
 14. A fuel injection valve according to claim 4, in which theprotective cap (20) is connected to the nozzle body (1) by indentations.15. A fuel injection valve according to claim 14, in which the axialdistance (31) is small relative to the diameter of the passage opening(29) of the protective cap (20).
 16. A fuel injection valve according toclaim 4, in which at least two inwardly protruding retention tongues(25) are formed on a periphery of the protective cap (20), theseretention tongues (25) engaging in an annular groove (23) of the nozzlebody (1).
 17. A fuel injection valve according to claim 16, in which theaxial distance (31) is small relative to the diameter of the passageopening (29) of the protective cap (20).
 18. A fuel injection valveaccording to claim 4, in which at least two inwardly protrudingengagement steps (22) are formed on a periphery of the protective cap(20), these engagement steps (22) engaging in an annular groove (23) ofthe nozzle body (1).
 19. A fuel injection valve according to claim 18,in which the axial distance (31) is small relative to the diameter ofthe passage opening (29) of the protective cap (20).
 20. A fuelinjection valve according to claim 4, in which the axial distance (31)is small relative to the diameter of the passage opening (29) of theprotective cap (20).